This invention relates to a fuel injection system for a two cycle engine and more particularly to an improved fuel injection nozzle arrangement for such an engine.
The advantages of fuel injection over carburetion are well known. Normally fuel injectors inject either directly into the combustion chamber (direct injection) or into the induction system (manifold or port injection). Each system has its own advantages and disadvantages. A difficulty with direct injection methods is that the fuel injector is subjected to the combustion chamber temperatures and pressure as the gases burn and expand. This dictates the use of expensive fuel injectors and also can give rise to the problem of servicing the fuel injector and maintaining its injection valve components free of foreign particles formed primarily by the combustion process.
Manifold injection, on the other hand, avoids the problems of direct cylinder injection but also loses many of the advantages of direct injection. That is, when direct cylinder injection is employed, it is possible to provide a stratified charge under low and medium speed running operations and hence both fuel efficiency and exhaust emission control are improved. However, with manifold injection, the ability to obtain stratification is substantially reduced due to the distance that the fuel charge flows from the injector into the combustion chamber.
Another type of fuel injector has also been proposed and may be used either with direct or manifold type of injection systems. This type of injector injects not only fuel under pressure, but also air under pressure. The air assists in dispersion and vaporization of the fuel particles. When utilized with either direct or manifold injection, the air fuel injectors have the same disadvantages as other types of fuel injectors. In addition, it is necessary with this type of injector to regulate the fuel and air pressure and provide separate valves for controlling the flow. Thus this type of injector is also more expensive, particularly if employed in conjunction with direct cylinder injection.
There are disclosed in the copending application of Masahiko Katoh and Masanori Takahashi, entitled "Fuel Injection System For Two Cycle Engine", Ser. No. 831,786, filed Feb. 5, 2992, still pending and assigned to the assignee hereof a number of embodiments of fuel injectors wherein the advantages of direct cylinder injection are employed without the disadvantages thereof by injecting fuel into the combustion chamber through one or more small nozzle ports formed in the cylinder liner and which are opened and closed by the movement of the pistons. Compressed air and fuel is supplied upstream of the nozzle port so as to provide an air fuel injection system which achieves stratification without the disadvantages of direct cylinder injectors and/or the prior art type of fuel air injectors.
Although the construction described in aforenoted copending application Ser. No. 831,786 has a number of advantages, for the most part, the embodiments of that application require the formation of the nozzle port in the cylinder wall or cylinder liner to be accurately positioned and sized. However, this means that servicing or replacement of the nozzle port is not easy and may, in fact, be difficult without completely disassembling the engine. Also, with the types of arrangement shown in that application, the amount of mixing of the fuel and air injected upstream of the nozzle port may be limited.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for a two cycle engine having the advantages of direct and manifold fuel injection without the disadvantages of either and wherein the device may be easily serviced.
It is a further object of this invention to provide an improved air fuel injector that does not require separate valving and control for the air and fuel relative to each other and which has the advantages of both manifold and direct injection without the disadvantages of either.